VexRiscv/src/main/scala/SpinalRiscv/Plugin/ShiftPlugins.scala

package SpinalRiscv.Plugin

import SpinalRiscv._
import spinal.core._
import spinal.lib.Reverse



class FullBarrielShifterPlugin extends Plugin[VexRiscv]{
  object ShiftCtrlEnum extends SpinalEnum(binarySequential){
    val DISABLE, SLL, SRL, SRA = newElement()
  }

  object SHIFT_CTRL extends Stageable(ShiftCtrlEnum())
  object SHIFT_RIGHT extends Stageable(Bits(32 bits))

  override def setup(pipeline: VexRiscv): Unit = {
    import Riscv._
    import pipeline.config._



    val immediateActions = List[(Stageable[_ <: BaseType],Any)](
      SRC1_CTRL                -> Src1CtrlEnum.RS,
      SRC2_CTRL                -> Src2CtrlEnum.IMI,
      REGFILE_WRITE_VALID      -> True,
      BYPASSABLE_EXECUTE_STAGE -> False,
      BYPASSABLE_MEMORY_STAGE  -> True,
      REG1_USE                 -> True
    )

    val nonImmediateActions = List[(Stageable[_ <: BaseType],Any)](
      SRC1_CTRL                -> Src1CtrlEnum.RS,
      SRC2_CTRL                -> Src2CtrlEnum.RS,
      REGFILE_WRITE_VALID      -> True,
      BYPASSABLE_EXECUTE_STAGE -> False,
      BYPASSABLE_MEMORY_STAGE  -> True,
      REG1_USE                 -> True,
      REG2_USE                 -> True
    )

    val decoderService = pipeline.service(classOf[DecoderService])
    decoderService.addDefault(SHIFT_CTRL, ShiftCtrlEnum.DISABLE)
    decoderService.add(List(
      SLL  -> (nonImmediateActions ++ List(SHIFT_CTRL -> ShiftCtrlEnum.SLL)),
      SRL  -> (nonImmediateActions ++ List(SHIFT_CTRL -> ShiftCtrlEnum.SRL)),
      SRA  -> (nonImmediateActions ++ List(SHIFT_CTRL -> ShiftCtrlEnum.SRA))
    ))

    decoderService.add(List(
      SLLI  -> (immediateActions ++ List(SHIFT_CTRL -> ShiftCtrlEnum.SLL)),
      SRLI  -> (immediateActions ++ List(SHIFT_CTRL -> ShiftCtrlEnum.SRL)),
      SRAI  -> (immediateActions ++ List(SHIFT_CTRL -> ShiftCtrlEnum.SRA))
    ))
  }

  override def build(pipeline: VexRiscv): Unit = {
    import pipeline._
    import pipeline.config._


    execute plug new Area{
      import execute._
      val amplitude  = input(SRC2)(4 downto 0).asUInt
      val reversed   = Mux(input(SHIFT_CTRL) === ShiftCtrlEnum.SLL, Reverse(input(SRC1)), input(SRC1))
      insert(SHIFT_RIGHT) := (Cat(input(SHIFT_CTRL) === ShiftCtrlEnum.SRA & reversed.msb, reversed).asSInt >> amplitude)(31 downto 0).asBits
    }

    memory plug new Area{
      import memory._
      switch(input(SHIFT_CTRL)){
        is(ShiftCtrlEnum.SLL){
          output(REGFILE_WRITE_DATA) := Reverse(input(SHIFT_RIGHT))
        }
        is(ShiftCtrlEnum.SRL,ShiftCtrlEnum.SRA){
          output(REGFILE_WRITE_DATA) := input(SHIFT_RIGHT)
        }
      }
    }
  }
}

class LightShifterPlugin extends Plugin[VexRiscv]{
  object ShiftCtrlEnum extends SpinalEnum(binarySequential){
    val DISABLE, SLL, SRL, SRA = newElement()
  }

  object SHIFT_CTRL extends Stageable(ShiftCtrlEnum())

  override def setup(pipeline: VexRiscv): Unit = {
    import Riscv._
    import pipeline.config._
    import IntAluPlugin._

    val immediateActions = List[(Stageable[_ <: BaseType],Any)](
      SRC1_CTRL                -> Src1CtrlEnum.RS,
      SRC2_CTRL                -> Src2CtrlEnum.IMI,
      ALU_CTRL                 -> AluCtrlEnum.BITWISE,
      ALU_BITWISE_CTRL         -> AluBitwiseCtrlEnum.SRC1,
      REGFILE_WRITE_VALID      -> True,
      BYPASSABLE_EXECUTE_STAGE -> True,
      BYPASSABLE_MEMORY_STAGE  -> True,
      REG1_USE                 -> True
    )

    val nonImmediateActions = List[(Stageable[_ <: BaseType],Any)](
      SRC1_CTRL                -> Src1CtrlEnum.RS,
      SRC2_CTRL                -> Src2CtrlEnum.RS,
      ALU_CTRL                 -> AluCtrlEnum.BITWISE,
      ALU_BITWISE_CTRL         -> AluBitwiseCtrlEnum.SRC1,
      REGFILE_WRITE_VALID      -> True,
      BYPASSABLE_EXECUTE_STAGE -> True,
      BYPASSABLE_MEMORY_STAGE  -> True,
      REG1_USE                 -> True,
      REG2_USE                 -> True
    )

    val decoderService = pipeline.service(classOf[DecoderService])
    decoderService.addDefault(SHIFT_CTRL, ShiftCtrlEnum.DISABLE)
    decoderService.add(List(
      SLL  -> (nonImmediateActions ++ List(SHIFT_CTRL -> ShiftCtrlEnum.SLL)),
      SRL  -> (nonImmediateActions ++ List(SHIFT_CTRL -> ShiftCtrlEnum.SRL)),
      SRA  -> (nonImmediateActions ++ List(SHIFT_CTRL -> ShiftCtrlEnum.SRA))
    ))

    decoderService.add(List(
      SLLI  -> (immediateActions ++ List(SHIFT_CTRL -> ShiftCtrlEnum.SLL)),
      SRLI  -> (immediateActions ++ List(SHIFT_CTRL -> ShiftCtrlEnum.SRL)),
      SRAI  -> (immediateActions ++ List(SHIFT_CTRL -> ShiftCtrlEnum.SRA))
    ))
  }

  override def build(pipeline: VexRiscv): Unit = {
    import pipeline._
    import pipeline.config._


    execute plug new Area{
      import execute._

      val isActive = RegInit(False)
      val isShift = input(SHIFT_CTRL) =/= ShiftCtrlEnum.DISABLE
      val amplitudeReg = Reg(UInt(5 bits))
      val amplitude = isActive ? amplitudeReg | input(SRC2)(4 downto 0).asUInt
      val shiftInput = isActive ? memory.input(REGFILE_WRITE_DATA) | input(SRC1)
      val done = amplitude(4 downto 1) === 0


      when(arbitration.isValid && isShift && input(SRC2)(4 downto 0) =/= 0){
        output(REGFILE_WRITE_DATA) := input(SHIFT_CTRL).mux(
          ShiftCtrlEnum.SLL -> (shiftInput |<<  1),
          default -> (((input(SHIFT_CTRL) === ShiftCtrlEnum.SRA && shiftInput.msb) ## shiftInput).asSInt >> 1).asBits  //ALU.SRL,ALU.SRA
        )

        when(!arbitration.isStuckByOthers){
          isActive := True
          amplitudeReg := amplitude - 1

          when(done){
            isActive := False
          } otherwise{
            arbitration.haltIt := True
          }
        }
      }
      when(arbitration.removeIt){
        isActive := False
      }
    }
  }
}